The mixtures carbon monoxide-hydrogen (CO/H.sub.2) and carbondioxide-hydrogen (CO.sub.2 -H.sub.2) are available from carbonaceous sources of non-petroleum origin, such as natural gas, by reforming with steam, and particularly coal by gasification. The production of hydrocarbons from synthesis gas, of which coal is the source, is expected to undergo considerable development.
This conversion has already been the subject of numerous research, but not giving entire satisfaction in the field of selectivity of the products formed.
A type of catalyst has been sought enabling the application of selective reactions with limitation of the growth of the chains of the products formed, and the use of carbon dioxide in place of carbon monoxide.
The use of carbon dioxide as carbon source has a fundamental interest, since CO.sub.2 is available in abundance, for example, in hydrogen production units, whereas it is generally rejected entirely into the atmosphere. The production of hydrocarbons from CO.sub.2 amounts consequently to economy of other carbon reserves whilst limiting rejects into the atmosphere as a source of pollution.
Catalysts based on copper and zinc are known at present as being the most effective systems in the synthesis of methanol. And recent investigations have shown that certain zeolite catalysts of the mordenite type are active in the conversion of methanol.
In French Pat. No. 2,320,923 catalysts have been proposed containing iron and copper on an ammonium Y type zeolite type support, for the synthesis of liquid hydrocarbons of the range of petrol and diesel fuel by the Fischer-Tropsch reaction.
In the same way, U.S. Pat. No. 4,180,516 and European Pat. No. 18,683 relate to the production of aromatic hydrocarbons from carbon monoxide and hydrogen in the presence of a heterogeneous catalyst, the first component being a chromium-zinc catalyst, the second being a zeolite of the ZSM type or a crystalline silicate of very specific composition, these catalysts being in admixture or separate.
On the other hand, according to French Pat. No. 2,019,913 the mordenite subjected to multiple alternate cycles of treatment with steam and of reflux in an inorganic acid is involved in a process for the conversion of hydrocarbons.